docstr: Write PID info to file.
docstr_tok: ["Write","PID","info","to","file","."]
code: def dump_pid_file(self):
      """
      Write PID info to file.
      """
      pid = os.getpid()
      filepath = os.path.join(
          CONF_HOME, "serving_" + str(self.args.port) + ".json"
      )
      if os.path.exists(filepath):
          os.remove(filepath)
      with open(filepath, "w") as fp:
          info = {
              "pid": pid,
              "module": self.args.modules,
              "start_time": time.time(),
          }
          json.dump(info, fp)
  
imports: import argparse
  import os
  import platform
  import json
  import multiprocessing
  import time
  import signal
  import paddlehub
  from paddlehub.commands import register
  from paddlehub.serving import app_compat
  from paddlehub.env import CONF_HOME
  from paddlehub.serving.http_server import run_all, StandaloneApplication
  from paddlehub.utils import log
  from paddlehub.utils.utils import is_port_occupied
  from paddlehub.server.server import CacheUpdater
label_desc: Use image node_id 1 for calling the ServingCommand obj's underlying member method code with example usage: obj.dump_pid_file() without return types